The headword is the neuter nominative, vocative, and accusative (and masculine accusative) singular form of the adjective polu/botos, -on; see LSJ s.v.
[1] The sense here is perhaps that the lemma is an epithet of regions, as is the final glossing word (cf. n.3). Nevertheless, Polybotos is a town in eastern Phrygia (Barrington Atlas map 62 grid F4), mentioned in Procopius, Secret History 18.42, where it appears in the accusative singular, and is thus identical in form with the headword.
[2] From the scholia on Aeschylus, Seven Against Thebes 774 (web address 1). A number of scholiasts to this verse, upon whom the Suda evidently relies, transmit this passage as an instance of the headword rather than polu/batos (much-trodden); cf. LSJ s.v.
[3] Literally oily or shining, but here in the figurative sense of a bountiful region. An example is Pindar, Isthmian Odes 2.20 (web address 2), liparai=s *)aqa/nais (in splendid Athens), perhaps alluding to the region's abundant olive trees; cf. LSJ s.v. liparo/s. Other Suda passages pertaining to the gloss are lambda 586, lambda 574, and lambda 575.